A lawn mower comprises, for example, a vehicle body, a blade assembly, and an actuator. The blade assembly is supported by the mower vehicle body via a floating mechanism so as to be able to lift out of and drop into an operating position in response to an external force exerted thereon. The actuator lifts the blade assembly from the operating position to a lifted position and keeps it in the lifted position. The actuator may be provided in the form of a fluid-pressure actuator unit into which an electric motor, a fluid-pressure pump, and a fluid-pressure cylinder are integrated.
JP2006-105226A, published by the Japan Patent Office in 2006, proposes a fluid-pressure actuator unit comprising an electric motor, a fluid-pressure pump, a fluid-pressure cylinder, and an operation check valve. The fluid-pressure pump is a double-discharge type, driven by the electric motor, and discharges pressurized fluid to drive the fluid-pressure cylinder to extend or contract. The operation check valve operates in response to a discharge pressure of the fluid-pressure pump so as to supply the discharged fluid to a corresponding fluid-pressure chamber in the fluid-pressure cylinder.